Question

Na is heated in air at $300{}^\circ C$ to form ‘X’. X absorbs $C{{O}_{2}}$ and forms $N{{a}_{2}}C{{O}_{3}}$ and Y. Which of the following is Y?
(A) ${{H}_{2}}$
(B) ${{O}_{2}}$
(C) ${{H}_{2}}{{O}_{2}}$
(D) ${{O}_{3}}$

Answer 1

Hint: The sodium metal will react to form a sodium peroxide in presence of ordinary air, which can quickly absorb carbon dioxide from the air. This leads to the formation of sodium carbonate and the byproduct Y.

Complete step by step solution:
- As we know, the element Sodium is typically quite reactive with air, and the reactivity is a function of the relative water-vapour content or humidity of the air. Also, the corrosion of solid sodium by air is enhanced by the presence of slight amounts of impurities in the sodium.
- Sodium reacts with excess of air which is free from carbon dioxide which means that sodium can react with excess of oxygen. In the question the step one reaction includes the heating of sodium in presence of air at a temperature around $300{}^\circ C$ and the product ‘X’ is being formed and this corresponding reaction can be written as follows
\[2Na+{{O}_{2}}\xrightarrow{300{}^\circ C}N{{a}_{2}}{{O}_{2}}\]
- Sodium reacts with oxygen to first form sodium oxide at a temperature around $200{}^\circ C$.When it further heated up to $300{}^\circ C$, sodium being larger in size does not have a positive field strong enough to prevent the further oxidation of oxide into peroxide, but strong enough to prevent the formation of superoxide. Thus the product sodium peroxide (X) is formed.
 - The step two reaction can be represented as follows
\[2N{{a}_{2}}{{O}_{2}}+2C{{O}_{2}}\to 2N{{a}_{2}}C{{O}_{3}}+{{O}_{2}}\]
-As we know sodium peroxide is an oxidizing agent and it absorbs carbon dioxide and oxidizes it to oxygen, thereby itself getting reduced to sodium carbonate. Hence Oxygen is Y.

Therefore the correct option is (B) ${{O}_{2}}$.

Note: Keep in mind that sodium is usually kept immersed in a nitrogen atmosphere or in inert liquids such as naphtha or kerosene since it does not react with nitrogen. The sodium is considerably more reactive in air as a liquid than as a solid, and the liquid can ignite at a temperature around about $125{}^\circ C$.